Valve timing adjusting apparatus

ABSTRACT

A valve timing adjusting apparatus includes a housing, a vane supporting portion, a vane member, a limiting member, a fitting hole, and an atmosphere communication hole. The housing is rotatable about a rotation axis. The housing includes a peripheral wall and side walls to define a receiving chamber. The vane member is received integrally with the vane supporting portion in the receiving chamber. The vane member defines an axial hole therein. The limiting member is reciprocably received in the axial hole. The fitting hole and the atmosphere communication hole are provided to one of the side walls. The fitting hole is communicated with atmosphere via the communication hole. The limiting member limits the vane member from rotating relative to the housing when one end of the limiting member is fitted with the fitting hole.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-290656 filed on Nov. 8, 2007 and Patent Application No. 2008-238613 filed on Sep. 17, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve timing adjusting apparatus for changing opening and closing timing of at least one of an intake valve and an exhaust valve for an internal combustion engine or an engine in accordance with an operational condition.

2. Description of Related Art

Conventionally, there is known a vane-type valve timing adjusting apparatus, which drives a camshaft via a timing pulley of a housing rotatable in time with a crank shaft of the engine, and via a chain sprocket. The above valve timing adjusting apparatus controls a phase relationship between the crank shaft and the camshaft using pressure of hydraulic oil that flows into an advance oil pressure chamber and a retard oil pressure chamber, which serve as pressure chambers (see, for example, JP-A-2003-201810 corresponding to US 2003/0121485).

In the above vane-type valve timing adjusting apparatus, because a stopper piston provided to a vane rotor is usually fitted with a fitting hole provided to the housing at the start of the engine, the vane rotor is limited from rotating relative to the housing. The above configuration is made to attempt reliable transmission of the driving force from the crank shaft to the camshaft immediately after the start of the engine, and to attempt the reduction of the noise due to the vibration caused by the rotation of the vane rotor relative to the housing.

At the time of unexpected stop of the engine, the operation of the engine may stop in a state, where the stopper piston is not fitted with the fitting hole of the housing. In the above case, at the restart of the engine in the next operation, it is required that variable torque of the camshaft be used to fluctuate the vane rotor such that the stopper piston is brought into a fitted relation with the fitting hole of the housing, and thereby the relative rotation of the vane rotor relative to the housing is limited.

In the conventional valve timing adjusting apparatus, the fitting hole of the housing is usually filled with hydraulic oil. Thus, when the stopper piston is brought into the fitted relation with the fitting hole, the stopper piston pushes back hydraulic oil in the fitting hole toward an oil passage. However, in a case, where the stopper piston has a tip end portion having a diameter larger than a diameter of the oil passage, pressure loss caused by the pushing of hydraulic oil by the stopper piston during the fitting of the stopper piston is large, and thereby response of the stopper piston speed is reduced. For example, in a case of the stopper piston that has a large tip end portion as shown in JP-A-2003-201810, the responsivity of stopper piston may remarkably deteriorate specifically when temperature is low, such as at the start of the engine, in which a degree of viscosity of hydraulic oil is large.

SUMMARY OF THE INVENTION

The present invention is made in view of the above disadvantages. Thus, it is an objective of the present invention to address at least one of the above disadvantages.

To achieve the objective of the present invention, there is provided a valve timing adjusting apparatus that is provided to a driving force transmission system for transmitting a driving force from a first shaft of an internal combustion engine to a second shaft that actuates at least one of an intake valve and an exhaust valve, wherein the valve timing adjusting apparatus adjusts opening and closing timing of the at least one of the intake valve and the exhaust valve. The valve timing adjusting apparatus includes a housing, a vane supporting portion, a vane member, a limiting member, a fitting hole, and an atmosphere communication hole. The housing is rotatable about a rotation axis with one of the first shaft and the second shaft. The housing includes a peripheral wall and side walls that are connected to both axial ends of the peripheral wall along the rotation axis. The housing defines a receiving chamber by the peripheral wall and the side walls. The vane supporting portion is received in the receiving chamber for being rotatable with the other one of the first shaft and the second shaft. The vane member is received in the receiving chamber. The vane member is provided integrally with the vane supporting portion. Pressure of working fluid, which flows into and out of pressure chambers of the receiving chamber, causes the vane member to rotate relative to the housing within a predetermined angle range. The vane member includes an axial hole that extends therethrough along the rotation axis. The limiting member is reciprocably received in the axial hole for limiting the vane member from rotating relative to the housing. The fitting hole is provided to one of the side walls of the housing for fitting with one end of the limiting member. The atmosphere communication hole is provided to the one of the side walls for communication with atmosphere. The fitting hole is communicated with atmosphere via the atmosphere communication hole. The limiting member limits the vane member from rotating relative to the housing when the one end of the limiting member is fitted with the fitting hole.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a cross-sectional view illustrating a valve timing adjusting apparatus according to the first embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1;

FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2;

FIG. 4 is a cross-sectional view illustrating the valve timing adjusting apparatus according to the first embodiment of the present invention in a state, where vane members are located at a full retard position;

FIG. 5 is a cross-sectional view illustrating the valve timing adjusting apparatus according to the first embodiment of the present invention in a state, where the vane members are located at a full advance position;

FIG. 6 is a cross-sectional view illustrating a valve timing adjusting apparatus according to the first modification of the present invention;

FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6;

FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 6;

FIG. 9 is a cross-sectional view illustrating a valve timing adjusting apparatus according to the second modification of the present invention;

FIG. 10 is a cross-sectional view taken along line X-X in FIG. 9; and

FIG. 11 is a cross-sectional view taken along line XI-XI in FIG. 9.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

A valve timing adjusting apparatus according to the first embodiment of the present invention is shown in FIGS. 1 to 5. A valve timing adjusting apparatus 10 is a hydraulic control apparatus that employs hydraulic oil as working fluid, and adjusts valve timing of an intake valve.

As shown in FIG. 1, the valve timing adjusting apparatus 10 includes a housing 11 and a vane rotor 50. The housing 11 includes a front plate 20 as a side wall, a shoe housing 30 as a peripheral wall, and a chain sprocket 40 as another side wall. The front plate 20, the shoe housing 30, and the chain sprocket 40 are coaxially fixed with each other through a bolt 12. Due to the above configuration, the front plate 20 and the chain sprocket 40 are coupled to both axial ends of the shoe housing 30 along a rotation axis. Thus, the shoe housing 30, the front plate 20, and the chain sprocket 40 define a receiving chamber 35 therebetween. The chain sprocket 40 is coupled to a crank shaft, which serves as a drive shaft (first shaft) of an engine (not shown), via a chain (not shown) such that a driving force is transmitted to the chain sprocket 40 for rotation of the chain sprocket 40 in time with or synchronously with the crank shaft.

The driving force of the crank shaft is transmitted to a camshaft 70, which serves as a driven shaft (second shaft), via the housing 11. The camshaft 70 opens and closes an intake valve (not shown). For example, the camshaft 70 actuates the intake valve for displacing the intake valve to an opening position and a closed position. The camshaft 70 is rotatably received in the chain sprocket 40 in a predetermined phase relationship relative to the chain sprocket 40.

The vane rotor 50 is received in the receiving chamber 35, and contacts an axial end surface of the camshaft 70 along the rotation axis. The camshaft 70 and the vane rotor 50 are coaxially fixed with each other via a bolt 13. The positioning of the vane rotor 50 relative to the camshaft 70 in a rotational direction is made through fitting a positioning pin 14 into the vane rotor 50 and the camshaft 70. The above configuration allows the vane rotor 50 and the camshaft 70 to coaxially rotate relative to the housing 11. The camshaft 70, the housing 11, and the vane rotor 50 clockwisely rotate when observed in a direction indicated by an arrow Z shown in FIG. 1. In the present embodiment, the above clockwise rotational direction is defined as an advance direction of the camshaft 70 relative to the crank shaft.

As shown in FIG. 2, the shoe housing 30 of the housing 11 includes a tubular portion 31, which has a tubular shape, and shoes 32, 33, 34, which radially inwardly project from the tubular portion 31. Each of the shoes 32, 33, 34 has a generally trapezoid shape, and the shoes 32, 33, 34 are arranged in generally equal intervals along a radially inner surface of the tubular portion 31 in the rotational direction.

The vane rotor 50 includes a hub portion 51, which serves as a vane supporting portion, and vanes 52, 53, 54, which serves as vane members. The vanes 52, 53, 54 are arranged in generally equal intervals along a radially outer surface of the hub portion 51 in the rotational direction. The vanes 52, 53, 54 are integral with the hub portion 51. The vane rotor 50 is received in the receiving chamber 35 such that the vane rotor 50 is rotatable relative to the housing 11. Each of the vanes 52, 53, 54 is rotatably received in a corresponding vane receiving chamber 351. The shoes 32, 33, 34 define three vane receiving chambers 351 in the receiving chamber 35, and the vane receiving chambers 351 are arranged in the rotational direction within predetermined angle ranges. In other words, the shoes 32, 33, 34 define the three vane receiving chambers 351 in the receiving chamber 35 such that the vane receiving chambers 351 are arranged one after another in the rotational direction. Also, each of the vane receiving chambers 351 circumferentially extends within the predetermined angle range.

Each of the vanes 52, 53, 54 divides the corresponding vane receiving chamber 351 into a retard oil pressure chamber and an advance oil pressure chamber as pressure chambers. In other words, the shoe 32 and the vane 52 defines a retard oil pressure chamber 301 therebetween, the shoe 33 and the vane 53 define a retard oil pressure chamber 302 therebetween, and the shoe 34 and the vane 54 define a retard oil pressure chamber 303 therebetween. Also, the shoe 34 and the vane 52 define an advance oil pressure chamber 311 therebetween, the shoe 32 and the vane 53 define an advance oil pressure chamber 312 therebetween, and the shoe 33 and the vane 54 define an advance oil pressure chamber 313 therebetween.

A seal member 15 is provided between (a) each of the shoes 32, 33, 34 and (b) a corresponding part of the hub portion 51, which part faces the shoe in the radial direction. Also, another seal member 15 is provided between (a) each of the vanes 52, 53, 54 and (b) a corresponding part of the tubular portion 31 of the shoe housing 30, which part faces the vane in the radial direction. The seal members 15 are fitted into grooves provided at tip ends of the shoes 32, 33, 34. The other seal members 15 are also fitted into other grooves provided at end portions of the vanes 52, 53, 54 opposite to the hub portion 51. For example, spring or other resilient member biases each seal member 15 toward the radially outer wall of the hub portion 51 or the radially inner wall of the tubular portion 31. Due to the above configuration, the seal members 15 fluid tightly keep the retard oil pressure chambers and the advance oil pressure chambers from each other. Thus, hydraulic oil is limited from leaking from one of the retard oil pressure chambers into adjacent one of the advance oil pressure chambers.

As shown in FIG. 1, the vane rotor 50 includes a hole 55 that is an axial hole extending through the vane 52 along the rotation axis or in a longitudinal direction. The hole 55 receives a stopper piston 80 and a spring 81 therein, and the stopper piston 80 serves as a limiting member. The stopper piston 80 has a generally hollow cylindrical shape, and is received in the hole 55 reciprocably displaceably in the longitudinal direction. The spring 81 has one axial end portion that contacts the chain sprocket 40 and another axial end portion that contacts the stopper piston 80. The spring 81 gives a force that is applied in the longitudinal direction. Due to the above configuration, the spring 81 biases the stopper piston 80 toward the front plate 20.

The front plate 20 has a recess groove portion 21 at an end surface of the front plate 20 toward the vane rotor 50, and the recess groove portion 21 receives a fitting ring 22 in a press fitted relation. The recess groove portion 21 is provided at a position generally intermediate between a full retard position and a full advance position. The full retard position and the full advance position are defined as maximum positions that the vane 52 is displaceable to when the vane rotor 50 rotates relative to the housing 11, for example. The fitting ring 22 has a generally hollow cylindrical shape. The fitting ring 22 has a fitting hole 23 at a generally central position thereof, which hole 23 extends through the fitting ring 22 in the longitudinal direction. In other words, the fitting hole 23 is provided at a position generally intermediate between the full retard position and the full advance position. The stopper piston 80 is capable of being fitted with the fitting ring 22 by fitting one end of the stopper piston 80 into the fitting hole 23.

Each of the stopper piston 80 and the fitting ring 22 has a fitting portion that is tapered. In other words, the stopper piston 80 has the fitting portion that is tapered such that the fitting portion becomes narrower toward the end compared with the other portion of the piston 80, for example. Also, the fitting ring 22 has the fitting portion that is tapered or is flared to have an enlarged inner diameter at the end, for example. Thus, the stopper piston 80 is capable of being smoothly fitted with the fitting ring 22. An oil pressure chamber 82 is defined at an outer periphery of the stopper piston 80 and is supplied with hydraulic oil. The pressure of hydraulic oil is applied in a direction such that the stopper piston 80 gets out of the fitting ring 22. The stopper piston 80 is brought into and is taken out of a fitted relation with the fitting ring 22 depending on a balance between (a) the force applied by the oil pressure chamber 82 and (b) the biasing force applied by the spring 81.

The recess groove portion 21 includes an atmosphere communication hole 24 that extends through the front plate 20 in a thickness direction of the front plate 20 or in the longitudinal direction. Due to the above configuration, the fitting hole 23 of the fitting ring 22 has an end portion opposite to the vane 52, which end portion is communicated with atmosphere via the atmosphere communication hole 24. In other words, the fitting hole 23 is exposed to atmosphere. It should be noted that the fitting hole 23 has another end portion toward the vane 52, which end portion is communicated with the receiving chamber 35.

As shown in FIG. 3, the atmosphere communication hole 24 has a diameter w1 that is smaller than a diameter w2 of a fitting end portion of the stopper piston 80, which end portion is fitted with the fitting hole 23. In other words, the diameter w1 of the atmosphere communication hole 24 is smaller than a diameter of the fitting hole 23. Due to the above configuration, an annular step surface 25 is defined between the atmosphere communication hole 24 and the fitting hole 23. Thus, when the stopper piston 80 is displaced in a direction for fitting with the fitting hole 23, the stopper piston 80 contacts the step surface 25.

As shown in FIGS. 2 and 3, an oblong groove portion 42 is formed at an end surface of the chain sprocket 40 toward the vane rotor 50. The oblong groove portion 42 has a generally arc shape and is recessed by a predetermined depth d. The oblong groove portion 42 is provided with a pressure discharge hole 41 that extends through the chain sprocket 40 in the thickness direction of the chain sprocket 40. Due to the above configuration, the hole 55 formed on the vane 52 is communicated with atmosphere via the oblong groove portion 42 and the pressure discharge hole 41.

Because the oblong groove portion 42 has the generally arc shape, even when the vane 52 is located at the full retard position as shown in FIG. 4, the oblong groove portion 42 is communicated with the hole 55. Also, even when the vane 52 is located at the full advance position as shown in FIG. 5, the oblong groove portion 42 is communicated with the hole 55. In other words, the hole 55 is communicated with atmosphere via the oblong groove portion 42 and the pressure discharge hole 41 regardless of the position of the vane 52 when the vane 52 is rotated relative to the housing 11 within the predetermined angle range defined between the full retard position and the full advance position. It should be noted that in FIGS. 2, 4, and 5, the fitting hole 23 and the atmosphere communication hole 24 formed on the front plate 20 are indicated by dashed and double-dotted lines for more obvious indication.

As above, the fitting hole 23 is formed in a range generally intermediate between the full retard position and the full advance position. The full retard position and the full advance position are maximum movable positions, on which the vane 52 is capable of being located when the vane rotor 50 is rotated relative to the housing 11. In other words, the fitting hole 23 is positioned within the movable range of the vane 52. Also, the oblong groove portion 42 is formed such that the oblong groove portion 42 is located within the movable range of the vane 52. Thus, the fitting hole 23 and the oblong groove portion 42 are always located at a position that correspondingly stays in a range within the outer edge of the vane 52 even when the vane 52 is displaced in a range between the full retard position shown in FIG. 4 and the full advance position shown in FIG. 5 by the rotation of the vane rotor 50 relative to the housing 11. In other words, fitting hole 23 and the oblong groove portion 42 are always located at a position that overlaps with the vane 52 in the longitudinal direction even when the vane 52 is displaced in a range between the full retard position and the full advance position.

As shown in FIG. 1, the vane rotor 50 has an end surface 56 toward the front plate 20, which surface 56 is fluid tightly slidable on the front plate 20. In other words, the vane 52 has an end surface toward the front plate 20, which surface is fluid tightly slidable on the front plate 20. Thus, the fitting hole 23 is limited from being communicated with the retard oil pressure chamber 301 or the advance oil pressure chamber 311, and thereby the leakage of hydraulic oil from the retard oil pressure chamber 301 or the advance oil pressure chamber 311 to atmosphere via the fitting hole 23 and the atmosphere communication hole 24 is reduced.

Also, similarly, the vane rotor 50 has an end surface 57 toward the chain sprocket 40, which surface 57 is fluid tightly slidable on the chain sprocket 40. In other words, the vane 52 has an end surface toward the chain sprocket 40, which surface is fluid tightly slidable on the chain sprocket 40. Therefore, the oblong groove portion 42 is limited from being communicated with the retard oil pressure chamber 301 or the advance oil pressure chamber 311, and thereby the leakage of hydraulic oil from the retard oil pressure chamber 301 or the advance oil pressure chamber 311 to atmosphere via the oblong groove portion 42 and the pressure discharge hole 41 is reduced.

As shown in FIG. 1, a radially outer wall of the camshaft 70 is rotatably supported by a bearing 16, and the radially outer wall of the camshaft 70 is provided with annular passages 71, 72, 73. The camshaft 70 and the hub portion 51 define a passage 821, three retard passages 305, and three advance passages 315 therein. The passage 821 is connected with the annular passage 71, the retard passages 305 is connected with the annular passage 72, and the advance passages 315 is connected with the annular passage 73.

As shown in FIG. 2, the hub portion 51 of the vane rotor 50 defines a passage 822 therein. The passage 822 connects the passage 821 with the oil pressure chamber 82. Due to the above configuration, the annular passage 71 and the oil pressure chamber 82 are communicated with each other via the passages 821, 822. Also, the hub portion 51 defines three retard passages 306 therein. Also, the retard passages 306 connect the retard passages 305 with the corresponding retard oil pressure chambers. Due to the above configuration, the annular passage 72 is communicated with each of the retard oil pressure chambers via the retard passages 305, 306. Furthermore, the hub portion 51 defines three advance passages 316 therein. The advance passages 316 connect the advance passages 315 with the corresponding advance oil pressure chambers. Due to the above configuration, the annular passage 73 is communicated with each of the advance oil pressure chambers via the advance passages 315, 316.

The oil pressure chamber 82 is connected to an oil pump (not shown) and an oil tank (not shown) via the passages 822, 821, and the annular passage 71. The oil pump feeds hydraulic oil pumped from the oil tank to the oil pressure chamber 82 via a control valve (not shown). When the oil pressure chamber 82 is fed with hydraulic oil, internal pressure in the oil pressure chamber 82 is increased, and thereby the stopper piston 80 gets out of or released from the fitting hole 23 of the fitting ring 22. Due to the above, the vane rotor 50 is disconnected from the front plate 20, and the vane rotor 50 is allowed to rotate relative to the housing 11.

When hydraulic oil in the oil pressure chamber 82 is discharged to the oil tank via the control valve, internal pressure in the oil pressure chamber 82 is reduced. As a result, the stopper piston 80 is biased toward the front plate 20 due to the biasing force of the spring 81.

The retard oil pressure chambers 301, 302, 303 are connected with the oil pump and the oil tank via the retard passages 306, 305, and the annular passage 72. Also, the advance oil pressure chambers 311, 312, 313 are connected with the oil pump and the oil tank via the advance passages 316, 315, and the annular passage 73. The oil pump supplies hydraulic oil pumped from the oil tank to the retard oil pressure chambers 301, 302, 303 or the advance oil pressure chambers 311, 312, 313 via a switching valve (not shown).

Also, each retard oil pressure chamber and each advance oil pressure chamber are connected to the oil tank via the switching valve. By switching the switching valve, hydraulic oil is supplied from the oil tank to one of (a) each retard oil pressure chamber and (b) each advance oil pressure chamber, and hydraulic oil is discharged to the oil tank from the other one of (a) each retard oil pressure chamber and each advance oil pressure chamber. Due to the above configuration, a relative rotational position of the vane rotor 50 relative to the housing 11 is changed depending on oil pressure balance, and the phase relation between the crank shaft (not shown) and the camshaft 70 is changed.

Next, one example of an operation of the present embodiment during a normal operation between the start of the engine and the stop of the engine will be described.

As shown in FIG. 2, when the engine is started, hydraulic oil from the oil pump (not shown) has not yet been fed to each retard oil pressure chamber, each advance oil pressure chamber, and the oil pressure chamber 82, and the vane rotor 50 is located at a position generally intermediate between the full retard position and the full advance position relative to the shoe housing 30. Because the stopper piston 80 is fitted with the fitting hole 23 of the fitting ring 22 in the above state, the vane rotor 50 is connected with the front plate 20, and thereby the vane rotor 50 is limited from being rotated relative to the front plate 20. Thus, the vane rotor 50 rotates with the front plate 20 or, in other words, rotates with the housing 11. Because the vane rotor 50 is connected with the front plate 20, the rotation driving force is reliably transmitted to the camshaft 70 from the crank shaft. Also, even when positive and negative variable torques are generated to the camshaft 70, the vane rotor 50 and the housing 11 are limited from generating vibration caused by the relative rotation, and thereby noise is limited from being generated.

During the normal operation of the engine, the operational state of the control valve (not shown) is switched such that hydraulic oil is fed to the oil pressure chamber 82 from the oil pump. When hydraulic oil is fed to the oil pressure chamber 82, and thereby the internal pressure in the oil pressure chamber 82 is increased, the stopper piston 80 gets out of the fitting hole 23 of the fitting ring 22. When the stopper piston 80 is taken out of the fitting hole 23, the vane rotor 50 is disconnected from the front plate 20, and thereby the vane rotor 50 becomes rotatable relative to the shoe housing 30 within the angle range defined between the full retard position and the full advance position. In the above case, when hydraulic oil is fed to the retard oil pressure chambers 301, 302, 303 from the oil pump, pressure of hydraulic oil in the retard oil pressure chambers 301, 302, 303 is increased, and the increased-pressure hydraulic oil pushes the vanes 52, 53, 54 in the retard direction. Due to the above configuration, the vane rotor 50 is rotated in the retard direction. Also, when hydraulic oil is fed to the advance oil pressure chambers 311, 312, 313 from the oil pump in contrast, pressure of hydraulic oil in the advance oil pressure chambers 311, 312, 313 is increased, and thereby the increased-pressure hydraulic oil pushes the vanes 52, 53, 54 in the advance direction. Due to the above configuration, the vane rotor 50 is rotated in the advance direction.

As above, hydraulic oil supplied from the oil pump to each retard oil pressure chamber or each advance oil pressure chamber controls the relative rotation of the vane rotor 50 relative to the housing 11. Due to the above configuration, the phase relation between the crank shaft (not shown) and the camshaft 70 is changed.

When the engine is commanded to stop in a state, where the stopper piston 80 is located on a side of the generally intermediate position in the advance direction, or in other words, the stopper piston 80 is located on a side of a formation position, on which the fitting hole 23 is formed, in the advance direction, hydraulic oil is caused to be discharged from the oil pressure chamber 82 and hydraulic oil is fed to each retard oil pressure chamber. More specifically, by changing the operational state of the control valve (not shown), hydraulic oil is discharged from the oil pressure chamber 82, and thereby internal pressure in the oil pressure chamber 82 is reduced such that the stopper piston 80 is biased toward the front plate 20 by the biasing force of the spring 81. Also, because hydraulic oil is fed to each retard oil pressure chamber in the above state, the vane rotor 50 is rotated in the retard direction, and thereby the stopper piston 80 is fitted into the fitting hole 23.

When the engine is commanded to stop in a state, where the stopper piston 80 is located on the other side of the formation position in the retard direction, hydraulic oil is caused to be discharged from the oil pressure chamber 82, and hydraulic oil is fed to each advance oil pressure chamber. Due to the above configuration, the vane rotor 50 is rotated in the advance direction, and thereby the stopper piston 80 is fitted into the fitting hole 23.

The operation of the engine is usually stopped in the above normal state, where the stopper piston 80 is fitted into the fitting hole 23, or in other words, where the vane rotor 50 is limited from being rotated relative to the housing 11, and thereby the engine is set ready for the restart.

Next, the operation of the present embodiment in an unexpected state, where the engine is restarted after the unexpected stop of the engine, will be described. The operation may be stopped in a state, where the stopper piston 80 is not fitted into the fitting hole 23, for example, when the engine is stopped unexpectedly. In the above case, if hydraulic oil remains in the oil pressure chamber 82 when the engine is restarted in the next operation, the remained hydraulic oil is caused to be discharged. Due to the above discharge, the stopper piston 80 is biased toward the front plate 20 by the biasing force of the spring 81. Also, in the above case, variable torque is generated to the camshaft 70. Due to the above, the vane rotor 50 fluctuates in the retard direction and in the advance direction. By the fluctuation of the vane rotor 50 in the retard direction and in the advance direction, the stopper piston 80, which is biased toward the front plate 20, is fitted into the fitting hole 23. As a result, the vane rotor 50 is connected with the front plate 20, and thereby the relative rotation of the vane rotor 50 relative to the front plate 20, in other words, to the housing 11 is limited.

In a conventional art, a limiting member is reciprocably displaceably received in an axial hole that includes a space defined by (a) an end portion of the limiting member opposite to the fitting hole and (b) the side wall of the housing. If the above space is closed in the conventional art, the followings may be expected. Specifically, when the limiting member is displaced in a direction for fitting with the fitting hole, a volume of the closed space is enlarged, and thereby pressure in the space is reduced. Thus, the above reduced pressure may restrict the limiting member from being displaced in the direction for fitting with the fitting hole. Also, when the limiting member is displaced in a direction for getting out of the fitting hole, the volume of the closed space is reduced, and thereby pressure in the space is increased. Thus, the limiting member may be restricted from being displaced in the direction for getting out of the fitting hole. As above, when the space is closed, the limiting member may be limited from being smoothly reciprocated.

As described above, in the first embodiment of the present invention, because the fitting hole 23 is exposed to atmosphere via the atmosphere communication hole 24, the fitting hole 23 does not store hydraulic oil. Thus, when the stopper piston 80 is brought into the fitted relation with the fitting hole 23, the fitting hole, which otherwise is required to push remained hydraulic oil toward the oil passage when the fitting hole were not exposed to atmosphere in the conventional art, is not required to push the remained hydraulic oil in the fitting hole 23. As a result, the stopper piston 80 is easily fitted into the fitting hole 23. As a result, responsivity of the stopper piston 80 is improved, and thereby the relative rotation of the vane rotor 50 relative to the housing 11 is easily and highly accurately limited due to the stopper piston 80. As a result, responsivity of the valve timing adjusting apparatus 10 is effectively improved, and thereby the phase of the camshaft 70 is highly accurately controlled.

In the first embodiment of the present invention, even under the low-temperature situation, in which degree of viscosity of hydraulic oil is high, such as the time of starting the engine, responsivity of the stopper piston 80 is made sufficiently high. Thus, even in the case of the restart of the engine after the unexpected stop, the relative rotation of the vane rotor 50 relative to the housing 11 is easily limited by the stopper piston 80.

Also, in the first embodiment of the present invention, the atmosphere communication hole 24 has the diameter w1 that is smaller than the diameter w2 of the end portion of the stopper piston 80, which end portion is fitted into the fitting hole 23. In other words, the diameter w1 of the atmosphere communication hole 24 is smaller than the diameter of the fitting hole 23. Due to the above configuration, the annular step surface 25 is formed between the atmosphere communication hole 24 and the fitting hole 23. When the stopper piston 80 is brought into the fitted relation with the fitting hole 23, the stopper piston 80 contacts the step surface 25 such that the stopper piston 80 is limited from ejecting or jumping out of the housing 11 through the atmosphere communication hole 24. Thus, even in a case, where the atmosphere communication hole 24 is formed in order to make the fitting hole 23 exposed to atmosphere, the stopper piston 80 is still limited from ejecting out through the atmosphere communication hole 24.

Furthermore, in the first embodiment of the present invention, the chain sprocket 40 is provided with the pressure discharge hole 41 that is communicated with atmosphere. The hole 55, in which the stopper piston 80 is reciprocably received, is communicated with atmosphere via the pressure discharge hole 41. Thus, even when the stopper piston 80 reciprocates in the hole 55, pressure in a space in the hole 55 defined between the stopper piston 80 and the chain sprocket 40 is kept similar to the atmospheric pressure. Due to the above configuration, the stopper piston 80 is smoothly reciprocably displaceable. Also, the hole 55 is communicated with atmosphere via the oblong groove portion 42 and the pressure discharge hole 41 regardless of the position of the vane 52 provided that the vane 52 is rotated relative to the housing 11 within the predetermined angle range. Thus, the stopper piston 80 is capable of being smoothly reciprocably displaceable regardless of the position of the vane 52. Thus, responsivity of the stopper piston 80 is effectively improved, and thereby the relative rotation of the vane rotor 50 relative to the housing 11 is easily and highly accurately limited by the stopper piston 80.

(First Modification)

A valve timing adjusting apparatus according to the first modification of the present invention will be described with reference to FIGS. 6 to 8. It should be noted that similar components of the valve timing adjusting apparatus of the present modification, which are similar to the components of the valve timing adjusting apparatus of the first embodiment, will be indicated by the same numerals, and explanation thereof will be omitted. The first modification is different from the first embodiment in that the end surface 56 and the end surface 57 of the vane rotor 50 have a recess and a seal portion, and in that the chain sprocket 40 does not include the oblong groove portion 42.

As shown in FIGS. 6 and 7, the vane 52 has a recess 521 and a seal portion 522 on the end surface 56 that faces the front plate 20 of the vane rotor 50. The recess 521 is formed by a recess groove 523 on the end surface 56. The seal portion 522 extends from the hub portion 51 along the outer edge of the vane 52 such that the seal portion 522 has a U shape, and the seal portion 522 is positioned to surround the recess 521 together with the hub portion 51. Also, the seal portion 522 is positioned around three ways or three sides of the seal members 15. The seal portion 522 contacts the front plate 20 such that the seal portion 522 is fluid tightly slidable on the front plate 20. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 301 and the advance oil pressure chamber 311 is reduced.

Similar to the above, the vane 53 has a recess 531 and a seal portion 532 on the end surface 56, and the vane 54 has a recess 541 and a seal portion 542. The seal portions 532, 542 contact the front plate 20 such that the seal portions 532, 542 are fluid tightly slidable on the front plate 20. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 302 and the advance oil pressure chamber 312, and leakage of hydraulic oil between the retard oil pressure chamber 303 and the advance oil pressure chamber 313 are reduced.

As shown in FIG. 8, the vane 52 has a recess 524 and a seal portion 525 on the end surface 57 that faces the chain sprocket 40 of the vane rotor 50. The recess 524 is formed by providing a recess groove 526 on the end surface 57. The seal portion 525 extends from the hub portion 51 along the outer edge of the vane 52 to have a U shape, and the seal portion 525 is positioned to surround the recess 524 together with the hub portion 51. Also, the seal portion 525 is positioned around the three sides of the seal members 15. In other words, the seal portion 525 is shaped to face the three sides of the seal members 15. The seal portion 525 contacts the chain sprocket 40 such that the seal portion 525 is fluid tightly slidable on the chain sprocket 40. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 301 and the advance oil pressure chamber 311 is reduced.

Similarly, the vane 53 has a recess 534 and a seal portion 535 on the end surface 571 and the vane 54 has a recess 544 and a seal portion 545 on the end surface 57. The seal portions 535, 545 contact the chain sprocket 40 such that the seal portions 535, 545 are fluid tightly slidable on the chain sprocket 40. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 302 and the advance oil pressure chamber 312, and leakage of hydraulic oil between the retard oil pressure chamber 303 and the advance oil pressure chamber 313 are reduced.

In the present modification, similar to the first embodiment, the fitting hole 23 is communicated with atmosphere via the atmosphere communication hole 24. Also, although the chain sprocket 40 does not include the oblong groove portion differently from the first embodiment, the chain sprocket 40 include the pressure discharge hole 41 that extends through the chain sprocket 40 in the thickness direction of the chain sprocket 40 similar to the first embodiment. Because the vane 52 has the recess 524 on the end surface 57, the pressure discharge hole 41 is communicated with the hole 55 via the recess 524 even when the vane 52 is located at one of the full retard position and the full advance position. In other words, the hole 55 is communicated with atmosphere via the recess 524 and the pressure discharge hole 41 regardless of the position of the vane 52 when the vane 52 is rotated relative to the housing 11 within the predetermined angle range defined between the full retard position and the full advance position.

The fitting hole 23 and the pressure discharge hole 41 are formed at a position generally intermediate between the full retard position and the full advance position. The above full retard and advance positions correspond to the maximum displaceable positions that the vane 52 is displaceable to when the vane rotor 50 is rotated relative to the housing 11. Thus, the fitting hole 23 and the pressure discharge hole 41 are always located a position correspondingly to the inward of the outer edge of the vane 52 when the vane 52 is located at any position between the full retard position and the full advance position. In other words, the fitting hole 23 and the pressure discharge hole 41 are always located to overlap with the vane 52 in the longitudinal direction when the vane 52 is located at any position between the full retard position and the full advance position, for example.

The seal portion 522 of the vane 52 contacts the front plate 20 such that the seal portion 522 is fluid tightly slidable on the front plate 20. Thus, the fitting hole 23 is limited from being communicated with the retard oil pressure chamber 301 or the advance oil pressure chamber 311, and thereby leakage of hydraulic oil from the retard oil pressure chamber 301 or from the advance oil pressure chamber 311 to atmosphere via the fitting hole 23 and via the atmosphere communication hole 24 is reduced. Similarly, the seal portion 525 of the vane 52 contacts the chain sprocket 40 such that the seal portion 525 is fluid tightly slidable on the chain sprocket 40. Therefore, the pressure discharge hole 41 is limited from being communicated with the retard oil pressure chamber 301 or the advance oil pressure chamber 311, and thereby leakage of hydraulic oil from the retard oil pressure chamber 301 or from the advance oil pressure chamber 311 to atmosphere via the pressure discharge hole 41 is reduced.

As described above, in the first modification, the vanes 52, 53, 54 are provided with the recesses 521, 531, 541 and the recesses 524, 534, 544, respectively. Thus, the vanes 52, 53, 54 slide on the front plate 20 through the seal portions 522, 532, 542, and the vanes 52, 53, 54 slide on the chain sprocket 40 through the seal portions 525, 535, 545. In other words, the vanes 52, 53, 54 slide on the front plate 20 and the chain sprocket 40 through slidable surfaces having substantially small areas. Thus, even when hydraulic oil is present in a clearance between (a) the vane 52, 53, 54 and (b) the front plate 20 or in a clearance between (a) the vane 52, 53, 54 and (b) the chain sprocket 40, hydraulic oil may generate small resistance, and thereby the vane rotor 50 is easily rotated relative to the housing 11. Specifically, although the degree of viscosity of hydraulic oil tends to be increased at the low-temperature situation, such as when the engine is started. However, in the first modification, even when hydraulic oil having high degree of viscosity is present in the clearance between (a) the vane 52, 53, 54 and (b) the front plate 20 or the chain sprocket 40, the vane rotor 50 is easily fluctuated and rotated relatively to the housing 11. As a result, responsivity of the vane rotor 50 is effectively improved, and the phase of the camshaft 70 is highly accurately controlled.

Also, in the first modification, the fitting hole 23 is exposed to atmosphere via the atmosphere communication hole 24, and the hole 55 is exposed to atmosphere via the pressure discharge hole 41. Thus, similar to the first embodiment, responsivity of the stopper piston 80 is effectively improved.

(Second Modification)

A valve timing adjusting apparatus of the second modification of the present invention will be described with reference to FIGS. 9 to 11. It should be noted that similar components of valve timing adjusting apparatus of the present example, which are similar to the components of the valve timing adjusting apparatus of the first modification, will be indicated by the same numerals, and explanation thereof will be omitted. Recesses and seal portions of the vanes 53, 54 of the second modification are different in shape from those in the first modification.

As shown in FIG. 10, the vane 53 has recesses 631 and a seal portion 632 on the end surface 56. The seal portion 632 radially outwardly extends from the hub portion 51 to have an I shape. The recesses 631 are formed by providing recess grooves 633 on both ends of the seal portion 632. Also, the seal portion 632 is positioned around the three sides of the seal members 15. The seal portion 632 contacts the front plate 20 such that the seal portion 632 is fluid tightly slidable on the front plate 20. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 302 and the advance oil pressure chamber 312 is reduced.

Similarly, the vane 54 has recesses 641 and a seal portion 642 on the end surface 56. The seal portion 642 contacts the front plate 20 such that the seal portion 642 is fluid tightly slidable on the front plate 20. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 303 and the advance oil pressure chamber 313 is reduced.

As shown in FIG. 11 the vane 53 has recesses 634 and a seal portion 635 on the end surface 57. The seal portion 635 radially outwardly extends from the hub portion 51 to have an I shape. The recesses 634 are formed by providing recess grooves 636 on both ends of the seal portion 635. Also, the seal portion 635 is positioned around the three sides of the seal members 15. The seal portion 635 contacts the chain sprocket 40 such that the seal portion 635 is fluid tightly slidable on the chain sprocket 40. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 302 and the advance oil pressure chamber 312 is reduced.

Similarly, the vane 54 has recesses 644 and a seal portion 645 on the end surface 57. The seal portion 645 contacts the chain sprocket 40 such that the seal portion 645 is fluid tightly slidable on the chain sprocket 40. Due to the above configuration, leakage of hydraulic oil between the retard oil pressure chamber 303 and the advance oil pressure chamber 313 is reduced.

Explanation of the recess 521, the seal portion 522, the recess 524, and the seal portion 525 shown in FIG. 9, FIG. 10 and FIG. 11 will be omitted because the configuration thereof are similar to those in the first modification.

As described above, also in the second modification, recesses are formed on both end surfaces of each vane along the rotation axis similar to the first modification. Thus, each vane slides on the internal wall surface of the housing 11 through the seal portion provided to the vane. In other words, the vane slides on the internal wall surface of the housing 11 through slidable surfaces having substantially small areas. In the case of the second modification, the areas of the slidable surfaces, through which the vane slides on the internal wall surface of the housing 11, are smaller compared with those in the first modification. Thus, even when hydraulic oil is present in a clearance between the vane and the internal wall surface of the housing 11, hydraulic oil generates substantially small resistance, and thereby the vane rotor 50 is easily rotated relative to the housing 11.

Other Embodiment

In the above embodiment, the oblong groove portion, which is communicated with the pressure discharge hole, has a generally arc shape. In the other embodiment of the present invention, the oblong groove portion is not limited to having the arc shape. However, the oblong groove portion may have any shape. Also, the oblong groove portion may have any depth.

Also, in the other embodiment of the present invention, each of the stopper piston and the fitting hole of the fitting ring may have a straight shape instead of the tapered shape.

In the above embodiment or the modifications, the front plate is provided with the fitting ring, and the stopper piston is fitted into the fitting hole formed on the fitting ring. In the other embodiment of the present invention, a fitting ring may be provided on the chain sprocket located opposite to the front plate, and the stopper piston may be fitted to the chain sprocket. Similarly, the pressure discharge hole may be formed on the front plate instead of the chain sprocket.

In the above embodiment or the modifications, the fitting ring is provided on the inner wall of the housing, and the stopper piston is fitted into the fitting hole formed on the fitting ring. In the other embodiment of the present invention, the fitting ring may not be formed on the inner wall of the housing. However, a fitting hole, which is communicated with atmosphere, may be formed on the housing such that the stopper piston is fitted into the above fitting hole.

In the above embodiment or the modifications, the valve timing adjusting apparatus is applied to the intake valve of the engine. However, the valve timing adjusting apparatus of the present invention may be applicable to an exhaust valve.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. A valve timing adjusting apparatus that is provided to a driving force transmission system for transmitting a driving force from a first shaft of an internal combustion engine to a second shaft that actuates at least one of an intake valve and an exhaust valve, wherein the valve timing adjusting apparatus adjusts opening and closing timing of the at least one of the intake valve and the exhaust valve, the valve timing adjusting apparatus comprising: a housing that is rotatable about a rotation axis with one of the first shaft and the second shaft, wherein: the housing includes a peripheral wall and side walls that are connected to both axial ends of the peripheral wall along the rotation axis; and the housing defines a receiving chamber by the peripheral wall and the side walls; a vane supporting portion that is received in the receiving chamber for being rotatable with the other one of the first shaft and the second shaft; a vane member that is received in the receiving chamber, wherein: the vane member is provided integrally with the vane supporting portion; pressure of working fluid, which flows into and out of pressure chambers of the receiving chamber, causes the vane member to rotate relative to the housing within a predetermined angle range; and the vane member includes an axial hole that extends therethrough along the rotation axis; a limiting member that is reciprocably received in the axial hole for limiting the vane member from rotating relative to the housing; a fitting hole that is provided to one of the side walls of the housing for fitting with one end of the limiting member; and an atmosphere communication hole that is provided to the one of the side walls for communication with atmosphere, wherein: the fitting hole is communicated with atmosphere via the atmosphere communication hole; and the limiting member limits the vane member from rotating relative to the housing when the one end of the limiting member is fitted with the fitting hole.
 2. The valve timing adjusting apparatus according to claim 1, wherein: the atmosphere communication hole has a diameter smaller than a diameter of the one end of the limiting member.
 3. The valve timing adjusting apparatus according to claim 1, further comprising: a pressure discharge hole that is provided to the other one of the side walls of the housing for communication with atmosphere, wherein: the axial hole is communicated with atmosphere via the pressure discharge hole regardless of a position of the vane member when the vane member is rotated relative to the housing within the predetermined angle range.
 4. The valve timing adjusting apparatus according to claim 3, further comprising. a groove that is provided to the other one of the side walls to face the vane member, wherein: the groove is communicated with the pressure discharge hole; and the groove is located at a position that overlaps with the vane member along the rotation axis when the vane member is positioned within the predetermined angle range. 